1. Field of the Invention
The present invention relates to a printhead substrate, a printhead, and a printing apparatus.
2. Description of the Related Art
A printing apparatus typified by a printer or the like prints by conveying a printing medium in a direction intersecting a scanning direction while scanning a printhead. The printhead includes a substrate (printhead substrate) on which printing elements such as electrothermal transducers (heaters) are arrayed.
A power supply voltage for driving each printing element is supplied onto the printhead substrate. For example, a power supply wiring (VH) and a ground wiring (GND) can be arranged respectively along the array direction of the printing elements. When printing, the more the number of printing elements to be driven concurrently, the more significant a drop in the power supply voltage.
Japanese Patent Laid-Open No. 2006-326972 discloses a structure in which the power supply wiring arranged along the array direction of the printing elements is connected to an electrode pad arranged at one end of the printhead substrate, and the ground wiring arranged along the array direction is connected to an electrode pad arranged at the other end of the printhead substrate. The power supply wiring and the ground wiring are arranged along the array direction of the printing elements. According to the structure disclosed in Japanese Patent Laid-Open No. 2006-326972, a difference in drop amounts in the power supply voltage between the respective printing elements is reduced.
As one method of increasing a printing speed, the number of printing elements to be driven at once is increased. As described above, however, the more the number of printing elements to be driven concurrently, the more significant the drop in the power supply voltage. Therefore, in order to increase the printing speed, it is necessary to increase the number of printing elements to be driven, and at the same time to prevent the drop in the power supply voltage resulting from this.
As one method of preventing the drop in the power supply voltage, the plurality of printing elements are divided into several groups, and the power supply voltages are supplied to the plurality of printing elements individually for each group. In the structure disclosed in Japanese Patent Laid-Open No. 2006-326972, a voltage is supplied from the power supply wiring (or the ground wiring) arranged along the array direction of the printing elements to each printing element. This makes it difficult to provide a path for supplying the power supply voltage for each group.